August 13, 2013

Researchers Successfully Turn A Meat-Eating Fish Into A Vegetarian

University of Maryland researchers announced last week they have been able to successfully turn a fish known for eating anything, the cobia, into a vegetarian.

While altering any animal’s diet may seem unnatural or even wrong, the biologists said the development could mean big bucks for the seafood industry.

“Aquaculture isn’t sustainable because it takes more fish to feed fish than are being produced,” said Aaron Watson, a graduate assistant at the university’s Center for Environmental Science. “But a new vegetarian diet might change everything.”

According to the research team’s report in the journal Lipids, the change occurred over the course of a four-year study using various mixtures of plant-based proteins and fatty acids and an amino acid-like substance. They were eventually able to create a substance that cobia and another farmed fish, gilt-head bream, actually ate. The researchers said the formulated diet sustained the two species as well as their natural diet.

Study co-author Allen Place said the findings should come as good news to both fish farmers and conservationists alike.

“This makes aquaculture completely sustainable,” he said. “The pressure on natural fisheries in terms of food fish can be relieved. We can now sustain a good protein source without harvesting fish to feed fish.”

The new study marks the first time science has been able to convert an omnivorous fish into an herbivore – despite numerous efforts.

After securing a grant from the National Oceanic and Atmospheric Administration (NOAA), Watson began trying to demonstrate cobia could subsist on a vegetarian diet in 2009. Watson said he believed a non-meat diet would also reduce the level of contaminants, such as polychlorinated biphenyls (PCBs) and mercury, absorbed by fish feeding in polluted waters.

To make the switch, the Maryland scientists replaced conventional fish meal with a food made of corn, soy and wheat. They were also able to replace fish oil in the two species’ diet using soybean or canola oil, supplemental lipids from algae sources, and amino acid supplements, such as taurine. Popular for being used in certain energy drinks, taurine is important to the metabolism of fats, responding to stress, and muscle growth in carnivorous fish.

Watson said he modeled the diet based on observations of herbivorous trout. For a period, he experiment with feeding the cobia barley.

“Cobia were very sensitive to it,” he told the Washington Post, noting the grain often passed through the fish undigested.

While the newly formulated feed pellets “are 15 to 20 percent more expensive than the commercially available feed,” the fish that ate them grew to a bigger average size, potentially offsetting any cost issues.

In addition to being more sustainable and cost effective, researchers said the artificial diet also makes the fish healthier to eat by reducing the amount of mercury and PCBs they ingest.

“Right now, you are only supposed to eat striped bass once every two weeks,” Place said. “You can eat aquaculture-raised fish twice a week because levels are so low.”